Discharge tube



Dec. 14, 1948. T, HAGENBERG DISCHARGE TUBE Filed Feb. 14, 1947 T. HAGENBERG AGENT Patented Dec. 14, 1948 2,455,993 r DISCHARGE TUBE.-

Theodorus Hagenberg, Eiridhoven, Netherlands, assignor to Hartford National Bank "and Trust Company, Hartford, Cn'n.,' as trustee Application February 14, 194,7,SerialNo. 723,496 I In the Netherlands July ,8, I944,

Section 1, Public Law 690, 'August s, 1946 Patent expires July 8, 1964 3 Claims.

In discharge tubes comprising a mercury cathode whose level is variable in operation, and a stationary igniting electrode which is partly immersed in mercury it may occur that the cathode mercury rises to such a level that it overflows and, by flowing through a transverse tube to another electrode, brings about a short-circuit. If the mercurywhich vaporises to the cathode is extracted from another electrode, there is the dangerthat in the case of complete vaporisation of the mercury of this electrode the discharge settles upon the lead-in of this electrode and this may lead to breakdown of the discharge tube. In orderto avoid this and other undesirable phenomena, the use of several means has been suggested, which have to ensure that the falling jet of mercury is divided into drops, or that the vaporisation of mercury to the cathode is counteracted. None of these means affords a definite guarantee against short-circuit or breakdown of the tube.

The present invention purports to provide a means whereby the tube is protected with security against short-circuit and complete vaporisation of an electrode. For this purpose the ignition electrode is surrounded by an insulating member whose lower edge is located above the level of the mercury. If, now, the mercury rises up to the lower edge of the insulating member which may consist, for example, of a little glass tube, the ignition electrode is covered thereby and rendered inactive. With such an undesired level of the mercury the tube can no longer be ignited and discontinues to function. An ignition will not be possible again before the level of the mercury has lowered till under the lower edge of the insulating tube. In definite cases it will be desirable, in addition to providing the insulating member according to the invention, to utilise one or more of the known means for maintaining a mercury level substantially constant. The invention is preferably applicable to discharge tubes whose cathode and anode both consist of mercury and which have the shape, for example, of an H. The igniting electrode used may be one of the known igniting members, for example a little rod dipped in the mercury of the cathode and consisting of material having a fairly high resistance, such as silicium carbide, or a thin walled tube of glass, quartz or similar material, which is filled with mercury or another conductor and which extends into the mercury of the cathode (so-called spark ignitor).

In order that the invention may be more clearly understood and readily carried into effect, it

will be described more fully by reference to the accompanying drawing.

The figure shows an H-shaped discharge tube comprising a mercury cathode l and a mercury anode 2. At the top of the cathode portion of the tube a spark ignitor is led-in by means of a metal cap 3, which ignitor consists of a little quartz tube 4 which is filled with mercury and which extends into the cathode mercury. Now, according to the invention, the spark ignitor is surrounded by a glass tube 5 which is sealed at the top to the metal cap 3 and which tightly surrounds at the bottom the spark ignitor. The lower edge of the tube 5 is located above the level of the mercury cathode. If, now, during the operation the anode vaporises more strongly than the cathode, the mercury of the cathode will rise. At the moment when the mercury of the cathode contacts with the lower edge of the tube -5, an ignition is no longer possible so that the tube discontinues to operate. Consequently, the use of the tube 5 prevents the mercury of the cathode from flowing over to the anode portion of the discharge tube and hence from bringing about a short-circuit. By tipping over the tube, the initial division of the mercury over the electrodes may be restored. The means according to the invention is also applicable to tubes of a construction different from that shown in the drawing, such as tubes in which the mercury which can raise the level of the cathode originates from a source of mercury other than the anode.

What I claim is:

1. An electric discharge device comprising a mercury cathode having a surface level subject to variations, an ignition electrode to initiate an electric discharge through said device from said cathode and having a portion immersed therein, and an insulating member surrounding said ignition electrodewithout the interposition of another electrode and having a lower edge portion near the surface of said mercury cathode, said lower edge portion being in contact with the cathode at a predetermined surface level thereof to prevent initiation of a discharge by said ignition electrode at cathode surface levels above said predetermined level.

2. An electric discharge device comprising a mercury cathode having a surface level subject to variations, an ignition electrode to initiate an electric discharge through said device from said cathode and having a portion immersed therein, and an insulating member surrounding said ignition electrode without the interposition of another electrode and having a lower edge portion spaced from said electrode with the inter edge thereof near the surface of said mercury cathode, said lower edge bein in contact with the cathode at a predeterminedsurface level thereofc to prevent initiation of a. discharge by said ignition electrode at cathode surface levels above said predetermined level.

3. An electric discharge device comprising a mercury cathode having a surface level subject to variations, a mercury anode, an ignition electrode to initiate an electricv discharge through said device from said cathode t0 said-anode and having a portion immersed in said cathode, and an insulating member surrounding said ignition electrode without the interposition of another electrode and having a lower edge portion near the surface of said mercury cathode, said lower edge portion being in contact with the cathode at a redetermined surface level thereof to prevent initiation of a discharge by said ignition electrode at cathode surface levels above said predetermined level.

THEODORUS HAGENBERG.

REFERENCES CITED .The following references are of record in the file of this patent:

'UNITED STATES PATENTS Name Date 2,106,857 Slepian Feb. 1, 1938 

